Control valve and fuel injection valve provided with same

ABSTRACT

A control valve and a fuel injection valve provided with same should be produced, in which it is possible to switch from a first operating state to a second operating state inexpensively and with short switching times, without requiring a hydraulic control line. To this end, a control valve is provided, which has a valve housing, a pressure chamber filled with electrorheological fluid, a displacing element that can slide in the valve housing and protrudes into the pressure chamber, and two electrodes that can apply an electrical field to the electrorheological fluid.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 35 USC 371 application of PCT/DE 00/04012 filed onNov. 10, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a control valve and a fuel injection valveprovided with same.

2. Description of the Prior Art

A fuel injection valve is disclosed in DE 197 35 232 in which a dampingchamber is provided, which can damp an opening motion of the nozzleneedle of the injection valve. The damping chamber is filled with anelectrorheological fluid and has an outlet around which two electrodesare disposed. By applying an electric field to the electrorheologicalfluid in the vicinity of the electrodes, the viscosity of the fluidthere can be varied. Correspondingly, the flow resistance changes, whichcounteracts an escape of the electrorheological fluid from the dampingchamber and consequently counteracts an opening of the nozzle needle. Inthis manner, by suitably producing the electrical field betweenelectrodes as a function of operating parameters of an internalcombustion engine in which the injection valve is used, influence can beexerted on the injection behavior of the injection valve.

SUMMARY OF THE INVENTION

The object of the invention is comprised in producing a control valve inwhich different injection cross sections can be produced in a fuelinjection valve.

A control valve according to the invention makes it possible to slow orcompletely inhibit the movement of the displacing element in a virtuallyarbitrary manner after it travels a particular distance. In this way,the opening behavior of the nozzle needle of a fuel injection valve canbe influenced in the desired manner, either directly or indirectly, forexample by means of an interposed fluid chamber, without requiring anadditional hydraulic control line; only one electrical connection isrequired for triggering the control valve according to the invention.

According to one embodiment of the invention, the displacing element isa plunger rod which protrudes into the pressure chamber. In thisembodiment, when the plunger rod is displaced, only a very slight volumeof electrorheological fluid is displaced. For this reason, it is nolonger necessary for there to be a buffer chamber with a variable volumewhich receives the displaced volume; solely the compressibility of theelectrorheological fluid makes the corresponding volume displacementpossible.

In another embodiment of the invention, the displacing element isprovided with a piston which closes the pressure chamber at one end, abuffer chamber is formed on the rear end of the piston, and the pressurechamber is connected to the buffer chamber by means of an overflowconduit. With this embodiment, when there is a small movement of thedisplacing element, a comparatively large volume of electrorheologicalfluid is displaced because the piston acts more or less as a booster.Conversely, this means that a relatively small flow resistance andattendant relatively low compressive forces in the electrorheologicalfluid suffice to produce a high resistance force counter to the movementof the displacing element.

A fuel injection valve according to one embodiment of the inventionoffers the advantage that a switching between different operating statescan be achieved for a low cost, in particular without a separatehydraulic control line. In particular, the electrically switchablecontrol valve makes it possible to brake or stop an opening stroke ofthe nozzle needle in a virtually arbitrary manner. This is particularlyadvantageous when the injection valve provides injection orificeselectability so that by selecting the opening stroke, differentinjection cross sections can be used.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in detail below in conjunction with theaccompanying drawings, in which:

FIG. 1 shows a schematic, sectional view of a fuel injection valveaccording to the invention, with a control valve according to a firstembodiment of the invention;

FIG. 2 shows a schematic, sectional view of a fuel injection valveaccording to the invention, with a control valve according to a secondembodiment;

FIG. 3 shows a schematic, sectional view of a fuel injection valveaccording to the invention, with a control valve according to a thirdembodiment;

FIG. 4 shows a schematic, sectional view of a fuel injection valveaccording to the invention, with a control valve according to a fourthembodiment;

FIG. 5 shows an enlarged schematic, sectional view of the control valveused in the fuel injection valve from FIG. 4,

FIG. 6 shows a schematic, sectional view of a fuel injection valveaccording to the invention, with a control valve according to a fifthembodiment; and

FIG. 7 shows an enlarged schematic, sectional view of the control valveused in the fuel injection valve from FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a fuel injection valve with a control valve according to afirst exemplary embodiment of the invention. The injection valveincludes a nozzle housing 10, which contains a nozzle needle 12 that canbe moved counter to the action of a restoring spring 14. The nozzlehousing 10 contains injection orifices 16 for the fuel to be injected,which is supplied by means of a supply line 18. The fuel can emerge fromthe injection orifices 16 as soon as the nozzle needle, starting fromits rest position in which it closes the injection orifices, hasexecuted an opening stroke in the direction of the arrow P. This openingmotion can be produced in various ways; the corresponding devices andprocesses are well known to the specialist in the field of fuelinjection systems and are also not the subject of the invention, so theyare not discussed further here.

The fuel injection valve is provided with a control valve 50 that has avalve housing 51 which contains a pressure chamber 52 and a bufferchamber 54 connected to the pressure chamber via overflow conduits 56.The pressure chamber, the buffer chamber, and the overflow conduits arefilled with an electrorheological fluid, i.e. a fluid whose viscositycan be locally influenced through the application of an electricalfield. Electrodes 58 are disposed in the vicinity of the overflowconduits 56 and can produce an electrical field which passes through theelectrorheological fluid in each overflow conduit.

From outside the control valve 50, a displacing element 60 protrudesthrough the buffer chamber into the pressure chamber 52. The displacingelement 60 is embodied here as a plunger rod which is connected to thenozzle needle 12. Consequently, an opening motion of the nozzle needle12 causes the displacing element 60 to be slid into the pressure chamber52, as a result of which a volume of electrorheological fluid isdisplaced from the pressure chamber 52, through the overflow conduits56, into the buffer chamber 54. The buffer chamber 54 can easily receivethis additional volume due to the compressibility of theelectrorheological fluid.

If no electrical field is present in the overflow conduits 56, byovercoming a comparatively low flow resistance, the electrorheologicalfluid can be displaced from the pressure chamber 52 into the bufferchamber 54 when the nozzle needle 12 executes an opening motion andthereby the displacing element 60 is slid into the pressure chamber 52.In order to influence the opening motion of the nozzle needle 12,however, control electronics (not shown) can produce an electrical fieldin the vicinity of the overflow conduits 56 at a desired time. Thisresults in a sharp increase in the viscosity so that a high resistanceis produced, counteracting a displacement of a volume of theelectrorheological fluid from the pressure chamber 52 into the bufferchamber 54. This can go so far as to prevent a volume displacement bymeans of the overflow conduits. In this manner, the opening movement ofthe nozzle needle 12 can be braked or even stopped at a desired timesimply by virtue of an electric field being generated in the vicinity ofthe overflow conduits 56.

Consequently, the electrorheological fluid in the electrical fieldfunctions like an adjustable throttle, which can also be completelyclosed as needed and therefore assumes the function of a valve. Ahydraulic stroke stop can thus be produced, whose magnitude and rigiditydetermines the end position of the nozzle needle in the opening stroke.

As an alternative to the overflow conduits 56 shown, an annular gap canalso be used when an inner annular electrode and an outer annularelectrode are used, the outer electrode being spaced apart from andencompassing the inner electrode.

FIG. 2 shows a fuel injection valve with a control valve according to asecond embodiment of the invention. When components are used in thisembodiment which are known from the first embodiment, the same referencenumerals are used. Please refer to the explanations made above withregard to their function.

In contrast to the first exemplary embodiment, in this instance, apiston 61 is embodied on the displacing element 60 and separates thepressure chamber 52 from the buffer chamber 54. In this embodiment, theoverflow conduit 56 is embodied in the valve housing 51 and, in the sameway as the prior embodiment, contains two electrodes 58, in order toproduce an electrical field in the vicinity of the overflow conduit.

With an opening motion of the nozzle needle 12, the piston 61 displacesa volume of electrorheological fluid from the pressure chamber 52,through the overflow conduit, and into the buffer chamber 54. The bufferchamber increases in size according to the movement of the piston sothat only the volume displaced by the sliding of the displacing element60 into the control valve must be accounted for by means of theelasticity and/or compressibility of the electrorheological fluid.

In the fuel injection valve according to the second embodiment, theopening behavior of the nozzle needle 12 can be influenced in the sameway as in the first embodiment by the resistance that opposes a volumedisplacement between the pressure chamber 52 and the buffer chamber 54due to the viscosity of the electrorheological fluid in the regionbetween the two electrodes 58.

FIG. 3 shows a fuel injection valve with a control valve according to athird embodiment of the invention. The same reference numerals are usedfor components which are known from the foregoing embodiments andreference is made to the explanations made above.

In contrast to the injection valves according to the first and secondembodiments, in which the opening motion of the nozzle needle isdirected toward the interior of the housing (inward opening valve), theinjection valve according to the third embodiment has a design in which,in order to open the injection orifices, the nozzle needle is movedoutward in the housing (outward opening valve).

On its front end, in addition to the injection orifices 16 that aredisposed along a circle on the same level, the nozzle needle 12 isprovided with injection orifices 17 which are likewise disposed along acircle. The injection orifices 17 are disposed further inside the nozzlehousing 10 than the injection orifices 16 so that with an opening strokeof the nozzle needle, the injection orifices 16 are opened first and theinjection orifices 17 are opened next.

In this embodiment as well, a piston 61 is used, which cooperates withthe displacing element 60 embodied as a plunger rod, which is anextension of the nozzle needle 12. The piston 61 displaces a fluid fromthe pressure chamber 52, through the overflow conduit 56, and into abuffer chamber 54 which in this embodiment, also contains the restoringspring 14.

The displacing element 60 is provided with a first control groove 62,which cooperates with a control edge 64 on the housing 10. The controlgroove 62 permits a connection from the pressure chamber 52 to theoverflow conduit 56 as long as the control edge 64 is not restingagainst the displacing element, i.e. starting from its rest positionshown in FIG. 3, this displacing element has not traveled a distancewhich corresponds to the distance measured in the axial directionbetween the control edge 64 and the end of the control groove 62oriented toward the pressure chamber.

On the displacing element 60, there is a second control groove 66 whichcooperates with a second control edge 68 in the housing. The secondcontrol groove 66 is not connected to the first control groove 62 and isoffset from it in such a way that its end oriented toward the controledge 68 protrudes further into the pressure chamber 52 than the end ofthe first control groove 62 oriented toward the first control edge 64.

The second control groove 66 permits a connection between the pressurechamber 52 and a collecting conduit 70, which leads to a collectingchamber 72. The two electrodes 58 which can generate an electrical fieldare disposed on the collecting conduit 70.

The above-described injection valve operates in the following manner:during a first phase of the opening motion of the nozzle needle 12, thepiston 61—particularly by means of the open control groove 62—displacesa volume of electrorheological fluid from the pressure chamber 52,through the overflow conduit 56, and into the buffer chamber 54. As soonas the end of the first control groove 62 meets the control edge 64,this displacement of fluid into the buffer chamber 54 is no longerpossible. The control groove 62 is embodied so that it is closed by thefirst control edge 64 after a stroke that is sufficient to open thefirst injection orifices 16.

After this first stroke, the electrorheological fluid can leave thepressure chamber 52 only via the second control groove 66, and can onlytravel toward the collecting chamber 72. This displacement of the fluidcan be influenced by the two electrodes 58 which, when necessary, canproduce such a high flow resistance of the electrorheological fluid thatit amounts to a closed second control groove. This means that it is notpossible for the nozzle needle 12 to execute a further opening strokeinto a position in which the second injection orifices 17 are opened.

By contrast, if the second injection orifices 17 need to be used inaddition to the first injection orifices 16, then the electrodes 58 arenot actuated so that the piston 61 can displace the electrorheologicalfluid from the pressure chamber 52, via the second control groove 64 andthe collecting conduit 70, and into the collecting chamber 72 so that itis possible for the nozzle needle 12 to execute an opening stroke into aposition in which both rows of injection orifices 16, 17 are used.

It is common to all of the embodiments described above that theelectrorheological fluid was displaced directly by a component connectedto the nozzle needle, namely the displacing element 60 and/or the piston61, when the nozzle needle had executed an opening stroke. Consequently,the opening stroke of the nozzle needle could be influenced because aninfluence was exerted on the flow resistance opposing a displacement ofa volume of electrorheological fluid.

The first and second embodiment have in common the fact that anactivation of the electrodes of the control valve must occur wheneverthe opening stroke of the nozzle needle is to be stopped. In contrast tothis, in the third embodiment, a choice can be made from the start as towhether it should be possible for the nozzle needle of the injectionvalve to open with only a first stroke or with a larger second stroke.If an opening with only a first stroke is desired, then the electrodesremain permanently activated; in contrast to the first and secondembodiment, namely, this state still permits a limited opening of thenozzle needle.

In the first and second embodiment, it is also possible to damp theopening stroke of the nozzle needle by means of the throttle actionproduced in the region of the overflow conduit so that a slower increaseof the injection rate is produced. The changing of the viscosity of theelectrorheological fluid in this connection occurs within such a shorttime that the needle damping can be changed even during the openingphase of the nozzle needle.

FIG. 4 shows a fuel injection valve with a control valve according to afourth embodiment of the invention. In this embodiment as well,components which are known from the foregoing embodiments are given thesame reference numerals and reference is made to the explanations above.

Like the first and second embodiments, the embodiment from FIG. 4 is aso-called inwardly opening injection valve, i.e. an injection valve inwhich in order to open, the nozzle needle must execute an opening strokethat is directed toward the interior of the nozzle housing 10. Thenozzle needle 12 is connected to a sliding element 20 in the form of apiston, which can be slid in a fluid chamber 22 that is filled withfuel.

An outlet conduit 75 branches off from the fluid chamber 22 and leads tothe control valve 50. This control valve is only schematically depictedin FIG. 4; the precise design is shown in FIG. 5. The control valve 50has a valve element 74 in the form of a cone, which can open or closethe outlet conduit 75. The valve element 74 is connected to thedisplacing element 60, which is once again embodied as a plunger rod.The displacing element is disposed so that in order to lift the valveelement, it must plunge further into the pressure chamber 52. In amanner comparable to the design known from FIG. 1, the opposingresistance is based on the fact that a variable resistance can beproduced to counteract a displacement of a volume of electrorheologicalfluid from the pressure chamber 52, through the overflow conduit 56, andinto the buffer chamber 54. In contrast to the embodiment of the controlvalve according to FIG. 1, in this embodiment, a compression spring 80is provided, which is disposed inside the pressure chamber 52, issupported on the displacing element 60 by a spring plate 82, and pushesthe valve element 74 into the position that closes the outlet conduit75.

It functions as follows: if the electrodes 58 are not activated and thedisplacing element 60 can therefore be slid into the pressure chamber52, then there is a comparatively large volume which can receive thefluid that is displaced by the sliding element 20 with an opening strokeof the nozzle needle 12. This results in a comparatively low rigidity ofthe hydraulic system involved in the displacement of fluid from thefluid chamber 22, which permits the nozzle needle 12 to execute anopening stroke into a position in which both the injection orifices 16of the first row and the injection orifices 17 of the second row areopened. By contrast, if the electrodes 58 are activated, then the valveelement 74 cannot be lifted up from the outlet conduit 75. As a result,there is a comparatively small volume for the hydraulic system, which isrelevant for a displacement of fluid by the sliding element 20, andthere is consequently a comparatively high rigidity of this hydraulicsystem, so that a pressure builds up in the fluid chamber 22 such thatonly a short opening stroke of the nozzle needle is possible. This canoccur through selective activation of the electrodes if the nozzleneedle 12 has executed enough of an opening stroke for just the firstrow of injection orifices 16 to open while the second row of injectionorifices 17 remains closed. The switching times for switching thecontrol valve between a state in which the outlet conduit 75 is open anda state in which the outlet conduit is closed are on an order ofmagnitude of less than one millisecond so that it is possible to switchbetween the different states during operation.

FIG. 6 shows a fuel injection valve with a control valve according to afifth embodiment of the invention. In this embodiment as well,components which are known from the foregoing embodiments are providedwith the same reference numerals and reference is made to theexplanations made there.

Similar to the third embodiment, this is an outwardly opening injectionvalve, i.e. an injection valve in which the nozzle needle executes anopening stroke which is oriented toward the outside of the nozzlehousing 10. Here, too, the nozzle needle 12 is provided with two rows ofinjection orifices 16, 17, which are opened depending on the magnitudeof the opening stroke. The control valve, which is used in the fuelinjection valve according to the fifth embodiment, is only schematicallydepicted in FIG. 6, and is shown in detail in FIG. 7, has a valveelement 74 which cooperates with an outlet conduit 75 of a fluid chamber22. Similar to the embodiment shown in FIG. 4, the valve element 74, byopening or closing the outlet conduit, serves to vary the rigidity ofthe hydraulic system, which counteracts a movement of the slidingelement 20. In contrast to the control valve shown in FIG. 5, thecompression spring 80 is disposed outside the pressure chamber 52.

The control valves that are used in the third, fourth, and fifthembodiments have in common the fact that only a very small volume isfilled with electrorheological fluid. This small volume ofelectrorheological fluid serves merely to control the switching motionof a valve element. The actual reaction on the nozzle needle 12 isproduced by a fluid which is separate from the electrorheological fluidand is preferably the fuel to be injected by the injection valve.

A particular advantage of the control valve according to the inventionlies in the fact that only a very small quantity of energy is requiredfor switching. This energy quantity can be drawn from the electricalenergy supply of a vehicle and is, moreover, largely recovered after theswitching event.

The foregoing relates to preferred exemplary of embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

We claim:
 1. A fuel injection valve comprising a nozzle housing (10), anozzle needle (12), a supply line (18) for supplying fluid into thenozzle housing (10), and a control valve (50), the nozzle housing (10)containing injection orifices (16) for the fuel to be injected, thenozzle needle (12) being capable of sliding in the nozzle housing (10)and being biased into a rest position in which it closes the injectionorifices (16), the control valve (50) including a valve housing (51), apressure chamber (52), a displacing element (60), and two electrodes(58), the pressure chamber (52) being filled with an electrorheologicalfluid, the displacing element (60) being supported for movement in thevalve housing (51) and protruding into the pressure chamber (52) andbeing coupled to the nozzle needle (12), the electrodes (58) beingadapted to apply an electrical field to the electrorheological fluid. 2.A control valve according to claim 1 wherein one of the electrodes (58)is disposed on one side of the pressure chamber (52).
 3. The controlvalve according to claim 2 wherein the displacing element (60) is aplunger rod which protrudes into the pressure chamber (52).
 4. Thecontrol valve according to claim 3 wherein the displacing element (60)is provided with a valve element (74) and wherein a compression spring(80) is provided, which pushes the valve element away from the pressurechamber.
 5. The control valve according to claim 2 wherein the pressurechamber (52) is provided with at least one overflow conduit (56) and theelectrodes are disposed in the vicinity of this overflow conduit.
 6. Thecontrol valve according to claim 2 wherein the displacing element isprovided with a piston (61) which closes the pressure chamber (52) atone end, wherein a buffer chamber (54) is formed on the rear end of thepiston, and wherein the pressure chamber is connected to the bufferchamber by means of an overflow conduit (56).
 7. The control valveaccording to claim 2 wherein the displacing element is provided with apiston (61) which closes the pressure chamber (52) at one end, wherein abuffer chamber (54) is formed on the rear end of the piston, and whereinthe pressure chamber is connected to the buffer chamber by means of anoverflow conduit (56).
 8. The control valve according to claim 1 whereinthe displacing element (60) is a plunger rod which protrudes into thepressure chamber (52).
 9. The control valve according to claim 8 whereinthe displacing element (60) is provided with a valve element (74) andwherein a compression spring (80) is provided, which pushes the valveelement away from the pressure chamber.
 10. The control valve accordingto claim 9 wherein the compression spring (80) is disposed in thepressure chamber (52).
 11. The control valve according to claim 10wherein the pressure chamber (52) is provided with at least one overflowconduit (56) and the electrodes are disposed in the vicinity of thisoverflow conduit.
 12. The control valve according to claim 8 wherein thepressure chamber (52) is provided with at least one overflow conduit(56) and the electrodes are disposed in the vicinity of this overflowconduit.
 13. The control valve according to claim 1 wherein the pressurechamber (52) is provided with at least one overflow conduit (56) and theelectrodes are disposed in the vicinity of this overflow conduit. 14.The control valve according to claim 13 wherein the overflow conduit(56) is constituted by an annular gap between the two electrodes (58).15. The control valve according to claim 1 wherein the displacingelement is provided with a piston (61) which closes the pressure chamber(52) at one end, wherein a buffer chamber (54) is formed on the rear endof the piston, and wherein the pressure chamber is connected to thebuffer chamber by means of an overflow conduit (56).
 16. The controlvalves according to claim 15 wherein the electrodes (58) are disposed onthe overflow conduit.
 17. The control valve according to claim 16wherein the displacing element (60) is provided with a first controlgroove (62) which is disposed so that it closes an outlet from thepressure chamber (52) after a first stroke of the displacing element(60), wherein the displacing element (60) is provided with a secondcontrol groove (66), which connects the pressure chamber to a collectingconduit (70) that leads to a collecting chamber (72), and wherein theelectrodes (58) are disposed on the collecting conduit (70).
 18. Thecontrol valve according to claim 15 wherein the displacing element (60)is provided with a first control groove (62) which is disposed so thatit closes an outlet from the pressure chamber (52) after a first strokeof the displacing element (60), wherein the displacing element (60) isprovided with a second control groove (66), which connects the pressurechamber to a collecting conduit (70) that leads to a collecting chamber(72), and wherein the electrodes (58) are disposed on the collectingconduit (70).
 19. The control valve according to claim 1 wherein thedisplacing element is provided with a piston (61) which closes thepressure chamber (52) at one end, wherein a buffer chamber (54) isformed on the rear end of the piston, and wherein the pressure chamberis connected to the buffer chamber by means of an overflow conduit (56).20. For a fuel injection valve including a nozzle housing (10), a nozzleneedle (12), a supply line (18) for supplying fluid into the nozzlehousing (10), the nozzle housing (10) containing injection orifices (16)for the fuel to be injected, the nozzle needle (12) being capable ofsliding in the nozzle housing (10) and being biased into a rest positionin which it closes the injection orifices (16), a control valve (50)comprising a valve housing (51), a pressure chamber (52), a displacingelement (60), and two electrodes (58), the pressure chamber (52) beingfilled with an electrorheological fluid, the displacing element (60)being supported for movement in the valve housing (51) and protrudinginto the pressure chamber (52) and being coupled to the nozzle needle(12), the electrodes (58) being adapted to apply an electrical field tothe electrorheological fluid.
 21. The injection valve according to claim20 wherein the displacing element (60) of the control valve is coupledto the nozzle needle (12).
 22. The control valve according to claim 21wherein the displacing element (60) is a plunger rod which protrudesinto the pressure chamber (52).
 23. The injection valve according toclaim 20 wherein the nozzle needle (12) is coupled to a sliding element(20) which protrudes into a fluid chamber (22) connected to the outletconduit (75), and wherein the control valve (50) is associated with thisoutlet conduit.
 24. The control valve according to claim 20 wherein thedisplacing element (60) is a plunger rod which protrudes into thepressure chamber (52).
 25. The control valve according to claim 20wherein the pressure chamber (52) is provided with at least one overflowconduit (56) and the electrodes are disposed in the vicinity of thisoverflow conduit.